The present invention relates to improvements in forming of particulates of metals and metalloids.
For many applications it is necessary that metals, including metallic alloys, and metalloids such as silicon and its alloys be provided in particulate form. Many systems have been devices for doing this. Among these is the centrifugal atomizer which exists in various forms. In known centrifugal atomizers the material to be atomized is fed onto the surface of a rotating disc-like member which may be dished or flat. In one form of such systems, a gas is used to cool the particles thrown off the rotating member by centrifugal forces. Representative of this type of system are U.S. Pat. Nos. 2,752,196, 4,053,264 and 4,078,873. Other systems rely on contact of molten droplets with a cooled surface.
The prior art systems known to applicants suffer from several disadvantages, especially when the metals or metalloids being processed have a high melting point. One disadvantage when gases are used for cooling is the volume of gas which must pass through the system to provide sufficient cooling capacity for solidification of the particles. Another disadvantage lies in the need for materials of construction of the apparatus which will withstand the temperatures encountered.
Additionally it has been discovered that properties of some alloys are altered by the speed with which the materials are cooled from the molten state. It is known that rapid cooling can be used to make amorphous alloys or metallic glasses. Some of the metallic glasses have been shown to exhibit properties which are quite different from the same materials in the crystalline state. A discussion of these materials is given in an article entitled "Metallic Glasses" by John J. Gilman, appearing in Science, volume 208, May 23, 1980 pages 856-861, and in an article of the same title by P. Chaudhari, B. C. Giesser and D. Turnbull appearing in Scientific American, Volume 242, (No. 4), April 1980 at pages 98-118.